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Encyclopedia > Constructive interference

Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). Absolute value snapshots of the (real-valued, scalar) wave field. As time progresses, the wave fronts would move outwards from the two centers, but the dark regions (destructive interference) stay fixed.
Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). Absolute value snapshots of the (real-valued, scalar) wave field. As time progresses, the wave fronts would move outwards from the two centers, but the dark regions (destructive interference) stay fixed.

Interference, also called "plasma (pattern)", is the superposition (overlapping) of two or more waves resulting in a new wave pattern. As most commonly used, the term usually refers to the interference of waves of the same or nearly the same frequency. Interference of two circular waves, snapshots of absolute value of (real,scalar) wave field for different wave lengths and distances of point sources File links The following pages link to this file: Interference Categories: GFDL images ... A wave crashing against the shore A wave is a disturbance that propagates. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...


The principle of superposition of waves states that the resultant displacement at a point is equal to the sum of the displacements of different waves at that point. If a crest of a wave meets a crest of another wave at the same point then the crests interfere constructively and the resultant wave amplitude is greater. If a crest of a wave meets a trough then they interfere destructively, and the overall amplitude is decreased. Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation. ...


Interference is involved in Thomas Young's double-slit experiment where coherent light (light which is in the same phase, and has the same frequency and wavelength) interferes to produce an interference pattern. More generally, this form of interference can occur whenever a wave can propagate from a source to a destination by two or more paths of different length. Two or more sources can only be used to produce interference when there is a fixed phase relation between them, but in this case the interference generated is the same as with a single source; see Huygens' principle. When a single source interferes with itself, the principle of conservation of energy dictates that the energy "missing" from the darkened regions of an interference pattern where destructive interference has taken place will be found in the brightened portions where constructive interference has taken place. Thomas Young, English scientist Thomas Young (June 13, 1773 – May 10, 1829) was an English scientist and researcher. ... The double-slit experiment consists of letting light diffract through two slits producing fringes on a screen. ... Phase, from the Greek phasis, meaning appearance, has a number of related meanings in English. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... The wavelength is the distance between repeating units of a wave pattern. ... Huygens principle (named for Dutch physicist Christiaan Huygens) is a method of analysis applied to problems of wave propagation. ... Conservation of energy (the first law of thermodynamics) is one of several conservation laws. ...


Light from any source can be used to obtain interference patterns, for example, Newton's rings can be produced with sunlight. However, in general white light is less suited for producing clear interference patterns, as it is a mix of a full spectrum of colours, that each have different spacing of the interference fringes. Sodium light is close to monochromatic and is thus more suitable for producing interference patterns. Most suitable is laser light because that is almost perfectly monochromatic. The phenomenon of Newtons rings is an interference pattern caused by the reflection of light between two surfaces - a spherical surface and an adjacent flat surface. ...


Constructive and destructive interference

When two waves superimpose, the resulting waveform depends on the frequency, (or wavelength) amplitude and relative phase of the two waves. If the two waves have the same amplitude A and wavelength the resultant waveform will have amplitude between 0 and 2A depending on whether the two waves are in phase or out of phase.

combined
waveform
Image:Interference of two waves.png
wave 1
wave 2

Two waves in phase Two waves 180° out
of phase

Consider two waves that are in phase,with amplitudes A1 and A2. Their troughs and peaks line up and the resultant wave will have amplitude A = A1 + A2. This is known as constructive interference. diagram drawn by Theresa Knott File links The following pages link to this file: Interference Categories: GFDL images ...


If the two waves are 180° out of phase, then one wave's crests will coincide with another wave's troughs and so will tend to cancel out. The resultant amplitude is A = |A1 − A2|. If A1 = A2 the resultant amplitude will be zero. This is known as destructive interference.


See also


  Results from FactBites:
 
Interference - Wikipedia, the free encyclopedia (529 words)
As most commonly used, the term usually refers to the interference of waves which are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency.
When a single source interferes with itself, the principle of conservation of energy dictates that the energy "missing" from the darkened regions of an interference pattern where destructive interference has taken place will be found in the brightened portions where constructive interference has taken place.
However, in general white light is less suited for producing clear interference patterns, as it is a mix of a full spectrum of colours, that each have different spacing of the interference fringes.
interference - definition of interference in Encyclopedia (514 words)
In communications, interference is anything which alters, modifies, or disrupts a message; as it travels along a channel, between a source and a receiver.
Interference is the superposition (overlapping) of two or more waves resulting in a new wave pattern.
Interference is involved in Thomas Young's double-slit experiment where coherent light (light which is in the same phase, and has the same frequency and wavelength) interferes to produce an interference pattern.
  More results at FactBites »

 
 

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